[c-nsp] NSF aware OSPF

[Siva Valliappan]

Hi Volodymyr,

please see inline:

On Thu, 9 Sep 2004, Volodymyr Yakovenko wrote:

> Hello!
>
>  According to SSO/NSF documentation in case of OSPF usage neighboring routers
>  should be "NSF-aware".
>
>  It looks like that for some equipment (like Cisco Catalyst 3550) IOS with
>  NSF-awareness functionality will not be ever available. It looks like there
>  is no any General Deployment NSF-aware IOS available.
>

as long as the C3550 ships off the 12.1E codebase there will be no support
for NSF-awareness for that platform.  please contact your account team
for future software roadmap plans for the C3550.

>  In case of ISIS there is 'Cisco configuration option' which brakes "all
>  routers in subnet should ne NSF-aware for NSF switchover" rule.
>

i fail to understand your question here.  there is only 1 IETF standard
for ISIS based graceful restart / awareness (unlike OSPF), so there should
be no interoperability issues as far as graceful restart awareness is
concerned.  however, for graceful restart capable devices like the
C12000, C10000, C6500 / C7600, C7500, C7300, we can operate in 2 modes
while using ISIS.  in one mode we make use of the standard ISIS
graceful restart mechanism.  now this is a "graceful" restart.  we
notify routing peers on a failover and continue forwarding on the old
forwarding table till the new routing table is rebuilt.  in the other
mode, we can actually failover in a "stateful" manner.  this is the
Cisco proprietary extension.  when failing over in a "stateful"
manner we do internal checkpointing of the ISIS topology, peer information,
etc.  we are therefore able to handle a failover in a manner that is
transparent to the rest of the network.  the other ISIS peers will
not know when a failover occurs as we do not do any special
signalling, etc (everything is handled internally).

so in neither of the above cases should other routers in a subnet
fail.  so can you please shed more light?  (unless i misunderstood the
question).

>  Does anyone know will such "Cisco" mode be available for OSPF or not?

in the case of OSPF there were 2 different IETF drafts for graceful
restart support.  Cisco implemented one, Juniper the other.  so Cisco
and Juniper do not interwork for OSPF based graceful restart currently.

cheers
.siva

>  Is there any technical reasons why it could not be implemented?
>
> --
> Regards,
> Volodymyr.
>
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